Conventionally, foam air ducts can be formed using sheets, such as in a twin-sheet forming method. When ducts with complex shapes are formed, including those with sharp or rounded corners, conventional formation of these ducts may cause a substantial amount of material to be wasted. This is because, conventionally, half of the complex shape comes in its final shape from the top sheet, and the other half comes in its final shape from the bottom sheet. Conventionally, each half is integrally and contiguously formed.